Potterton Suprima 50L problems

[Kevin]

Hi all, I've read the messages from 2006 and before regarding potterton boilers. I have a Suprima 50L which is "locking out" (showing as a red LED). The boiler tries to fire up, initiates, lights, runs for about 15 seconds and then locks out again. Now the reason for posting is that the engineers have been out twice and replaced the circuit board within the boiler and the air pressure switch. They run a quick test, i.e. turn it off and then turn it back on again, and the boiler always fires up. The infuriating thing is that as soon as they have gone, the boiler locks out again (after about an hour). This has been ongoing for about 2 weeks now and is costing a fortune in repairs.

I think that it is not the boiler itself, but the honeywell control unit that runs the programme. Should I get this replaced as well?

Kevin.

[John Stumbles]

Do you mean that the red LED flashes twice a second whilst the green LED is off?

I assume you mean they replaced the OCB on one occasion and the APS on another (rather than replacing the PCB twice)?

Why do you think that is to blame: how could it cause the observed problem?

[John Stumbles]

Oops I mean PCB. To replace it on the first occasion is reasonable for this boiler. If they replaced it with a Potty one rather than one of Geoff/CET's recons there is a possibility that the new one is also faulty. In any case I wouldn't suspect the APS (but maybe I haven't RTFMed hard enough) and I certainly would want to do more than "a quick test" (how quick?) to satisfy myself that the system's working properly.

The manual's fault-finding section seems to be a chocolate teapot on this: it only deals with what the boiler does from switch-on, not what may occur after a while. I'd be thinking what could cause a genuine lockout, maybe ignition problem or gas supply or gas valve problem.

[geoff]

In message , Kevin writes

please don't call them engineers

Did they leave the original HT lead and is it red ?

It sounds like it's not flame sensing properly. If the pcb has been replaced, then the next thing to suspect is the HT lead which is used by the pcb to sense that the flame is alight

NOTE TO JOHN, ED et al.

Any time you come up against a Suprima with a red HT lead, it's a common reason for flame sense failure -it's carbon fibre, not wire and shouldn't be trusted

[John Stumbles]

Thanks Geoff - noted

[Ed Sirett]

Thanks. I would have probably thought this is a flame sense problem if the boiler goes for only 15 seconds, but I would have missed the HT lead problem.

[geoff]

In message , Ed Sirett writes

Ah - that's one instance where the Suprima is fairly specific and consistent (although I have come across exceptions)

It will spark 13 times then shut off the GV and fan

it then sequences through again twice more

it then goes into lockout

[Doctor Drivel]

Maxie, what are you actually saying? Replace the lead type for type, or one which is copper? Is a copper lead available ? You appear to indicate so by mentioned some leads are "red".

[geoff]

In message , Doctor Drivel writes

replace the red carbon fibre lead with a wire one

Potterton are also replacing them as quickly and quietly as they can

The new modules come with a metal HT lead

[Kevin]

This sounds like the problem that I am having. The boiler initiates (fan whirring) then I hear the boiler ignite and see flame through the window, it continues to burn for short time and then stops. The LED then flashes red. However this is so random, for example, it sometimes starts as timed in the morning and runs the programme, then in the evening it will not start, cycling through the lockout, ignite, lockout process.

Kevin.

[Kevin]

Guys,

Thanks for the enlightening discussion of my problem. I'm about to call out the engineers again today and I'll discuss what you have said with them when they turn up.

Thanks again.

Kevin.

[geoff]

In message , Kevin writes

Then, you would have been better just replacing the pcb and the HT lead yourself - prolly cheaper and just as reliable as calling out a clueless fitter who'll do that anyway